Diets–Jongmans Syndrome due to a Novel KDM3B Variant: The First Molecularly Confirmed Case from Türkiye

Introduction: Diets–Jongmans syndrome is a rare neurodevelopmental disorder associated with heterozygous variants in KDM3B. The phenotypic spectrum continues to expand as additional individuals are identified. Case Presentation: We report an 8-year-old girl who presented with short stature, micrognathia, a pointed chin, and mild developmental delay. Exome sequencing (ES) revealed a novel likely pathogenic heterozygous nonsense variant, KDM3B (NM₀16604. 4) c. 5068C>T p. (Gln1690Ter), which was also detected in her mother. Biochemical evaluation revealed growth hormone deficiency, which was confirmed by two stimulation tests. Short stature without intellectual disability was noted in the mother, indicating intrafamilial phenotypic variability. Conclusion: This case represents the first molecularly confirmed Diets–Jongmans syndrome patient from Türkiye and adds further clinical observations regarding growth hormone deficiency in a patient with DIJOS.